12 Volt Missing at the Coil

[JJ 911SC]

After finishing detailing the car (1983 SC with an updated 1986 3.2L Engine) inside/out and replacing the Air Filter, I started the car. It idle for 5 minutes and I took it for a ride. At the end of the driveway, the engine "died". Push her back and start faultfinding.

I pull a spark plug wire out a plugged an old spark plug and crank it, there was no spark. Check for 12 Volt at the coil and it is missing.

As read in a faultfinding guide, I put 12 volts directly to the coil and the car started.

I check all the fuses and find one that was physically broken (not blown) but it was for the Engine Fan Compartment, which now works.

I "borrow" an ignition but the problem remains. New spare Fuel Pump Relay did not fix the problem either. Also, the grounding strap was broken on the engine relay panel (on the left) but the problem remains.

It could be as simple as a wiring problem that could be hard to trace as the car was an electrical mess when the previous owner bought it.

Before having this problem, I ordered the Hayes repairs book but it still in the mail (I order Hayes because one book cover the 1983 Model and the 1986 engine (up-grade) as where I would have need 2 books with Bentley, 1978-1983 & 1984-1989 and the previous owner bought the Bentley books but having moved twice in the last year, he is still going through the boxes…

I need to know the 12-volts path from the battery to the coil so I can find out if the DME relay or Control Unit (fitted under the passenger seat…) plays a role in this problem (I have an Electrical Diagram but don't seem to be able to attach).see Electrical Schematic)

Thanks

J.J.

[Tyson Schmidt]

EDIT: did not notice that it is an engine swap car.

First thing to check is the DME relay under the seat. (Or wherever they installed it in this case)

[JJ 911SC]

Hi Tyson

2 of the 3 book I order came in... "101 Project for Your Porsche 911" & "Porsche 911 Performance Hanbook 1963-1998" (3rd edition, brand new). I'm still waiting for the most important one the repair book "Porsche 911, 1965-1989".

The DME Control Unit (911 618 111 05) is under the passenger seat... and I did buy a DME Relay (911 618 154 00) but I would prefer to do some check before I plug it in. Any suggestion until I get my book?

Cheers

J.J.

[kidrock]

Recommend the DME relay swap. It is almost always the first thing done when a 3.2 encounters engine problems.

[dshepp806]

Originally Posted by kidrock

Recommend the DME relay swap. It is almost always the first thing done when a 3.2 encounters engine problems.

+1,..and the results would be (possibly) instantaneous? How old is the DME relay?


Doyle

[JJ 911SC]

Can't beleive how fast this is evolving...

I will swap the DME relay first thing tomorow morning and hopefully that will do it.
The car is a 44 years dream come true, I was 7 was my older (and rich cousin) drove a 1964 911 and I said that one day...

[JJ 911SC]

Well... Put a new DME relay and a Gas Pump Relay with the same result. So I decided to re-start from scratch.

So I decided to re-check the fuse box but using voltage vice continuity. One fuse had 12 Volts on one side but 0 Volt on the other side post. I check in the middle of the fuse and 12 Volts was present but nothing on the post, I took a close look at the fuse and it was physically broken (not melted) at one end (this is as per the one that was on the Engine Compartment Blower) .

So I put a new fuse in (Indicator Signal and Back Up Light position) and turn the ignition and "voilas" the engine started... but would not stop even when I took the key out (had to unplug the DME relay to get it stop).

I started to go over all the events... When the car first stall, my first step was to check the fuse box, right away I noticed that there was NO fuse in the "Fuel Pump" location so I though that it had sprung out and it would fix the problem but it did not.

So I decided to remove the Fuel Pump fuse. So I'm back to the way when I got the car. It's starting and stopping as per normal and there is no fuse in the Gas Pump position.

If you got a Fuel Pump relay is there also supposed to be a fuse in the Gas Pump position? The car is running as per normal without one.

Tanks to all involve

J.J.

[kidrock]

I may be wrong, but it may be possible you have some wiring issues due to the 3.2 conversion done by the PO?

[JJ 911SC]

Kidrock

I think this may be the case... When the car come back to Ottawa, ther previous owner took it to a specialized shop which started to work on it but stop because of numerous electrical problem. He had someone else clean it up and returned to the shop. I pick the same shop for the PPI and compression test. They remember the car and it electrical problems.

My next project is to clean up the electrical. Since it suspect that is has been running for quite a few years without a fuse in the Fuel Pump position, I'll continue until I figure what happened.

[JJ 911SC]

I think this may be the case... When it come back to Ottawa , the previous owner took it to a specialized shop which started to work on it but stop because of numerous electrical problem. He had someone else clean it up and returned to the shop. I pick the same shop for the PPI and compression test. They remember the car and it electrical problems.

My next project is to clean up the electrical. Since it suspect that is has been running for quite a few years without a fuse in the Fuel Pump position, I'll continue until I figure what happened.

[kidrock]

I'm definitely no expert, but I'm gonna take a WAG...and the more experienced contributors can correct me if I'm wrong.

IIRC, a stock SC has a fuse and a relay to the fuel pump. A 3.2 will probably have a fuse to the actual DME (the ECU/brain), while the DME relay acts as the "relay" to both the fuel pump AND the numerous sensors (CHT, O2, Speed and Reference sensors).

That may be the reason your SC fusebox is absent the fuse to the fuel pump.

I am basically an electrical idiot. Your best bet is time and patience...in essence, you may have to pull one fuse at a time, and test each system to find out which fuse affects which particular system. Get a piece of paper or cardboard, and make a diagram of your fuse system and keep it in a safe place for future reference. If you still have the plastic safety cover for your fusebox, you may want to place your reference guide inside the box.

Good luck, and Happy Hunting.

[kidrock]

P.S.---you have a vehicle known on this BBS as a "Frankenporsche" (this is not necessarily a derogatory term; no slight intended toward you or your vehicle.)

I noticed you plan to pick up a couple of books which are highly recommended by the more knowledgeable people here.

One recommendation: pick up the Bentley manual for 1984-1989 911's. This will help you with your drivetrain, and most everything else for your car. However, since there have been some major modifications to your car, the Bentley (which is very close to the Porsche shop manual) will not be able to help you in every case. But it's a manual you can't do without.

[JJ 911SC]

Kidrock

Don't worry no offense taken.

When I bought the car, the previous owner did mention the previous owner was an electrician and had wire going everywhere. The garage that did my PPI & Compression test did mention that they had work on the car 6 years ago and it was an electrical mess. While the German are known for their engineering when it comes to Electrical they are barely ahead of the Brits... I was an electronic tech for the Navy so I can follow a schematic and I already started to cleaned the mess up.

As for the car, it is running well (without a fuse in the Fuel Pump position) and it look great. Earlier today, I attend my first organized car show and pick up 3rd place in the "import" division, second to a 1985 model (red one).

Should I had followed the recommendation from the Remtech contributor (to check the fuse box for Voltage in & Voltage out), this thread would not exist but I learn quite a bit and now have a spare Fuel Pump and DME relays in the glove box which seem to be the normal Standard Operating Procedure.

2 of the book are in; "101 Project for Your Porsche 911" & "Porsche 911 Performance Handbook 1963-1998" (3rd edition, brand new). The 3rd one, Haynes, covers all the Porches in one book is in back order. The previous owner has the pre 1983 and post 1984 Bentley books somewhere in a moving box and I will get them soon.


Cheers

JJ

[kidrock]

sounds as if you have it sorted out, very well. Congratulations on your placing in the car show, and good luck.